If they want to take the train to Como San Giovanni and bus (or ferry) to Menaggio from there, the direct train is a cross-border EC train, and there are discounts for advance purchase on SBB. For example, a ticket for travel on July7, if bought today, is 34 CHF on the Sparangebot offer, instead of the normal 68 CHF regular fare. Note that these Special Offer tickets are non-refundable and good only on the one train purchased.
And if they want to get off the train in Lugano, still in Switzerland, and take the bus from there, I see Sparbillet tickets for 42 CHF for June 30 and July 2. Is this the ticket that is released 60 days in advance in limited numbers? I thought that was a SuperSaver ticket.